Transformer insulation



Dec. 26, 1933.

A. w, THOMPSON TRANSFORMER INSULATION Filed Oct. 29, 1952 2 Sheets-Sheetl 2 WITNESSES:

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` voltage transformers or Patented' Dec. 26, 1933 Arthur W. Thompson,

Westinghouse Electric pany, East Pittsburgh, Pa.,

Y Pennsylvania I Application 0otober`29,

r rnANsFonrn-:n INSULATION Sharon, Pa., assigner to & Manufacturing Comacorporation of 1932,.' serial No; 640,116

comms. (cl. 17a-35s) j My invention relates to insulation for electrical. apparatus and particularly to the construction and arrangement of .the insulating barriers associated with multiple coil transformer windings .which utilize nested barriers of insulating material, a

The improved barrier construction of my invention is particularly adapted for application to high-voltage oil-insulated surge-proof transformers, although it may also be applied to lowto air-insulated transformers. The invention is' described more in detail as applied to shell-type transformers although the principles thereof are also applicable to coretype transformers.

-In a copending application Serial No. 567,210 by'I-Ienry V. Putman,

ufacturing Company, there is described an irnproved arrangement of the various parts of a transformer winding and ofthe solid insulating material associated therewith which effects maximum dielectric strength for a given amount of insulating material. When constructed in accordance with the teachings ofthis application, a transformer is highly resistive to surge voltages. Such a transformer comprises' windings made up of a number of iiat coils of different sizes which are so insulated by a series of nested insulating barriers that the number of layers .of insulating material between any two points on the winding sulation can occur only V completely eectlve or between a point on the winding and ground is proportional to the voltage stress between these points. The insulating barriers, which are arl ranged to substantially follow the equipotential surfaces of the electrostatic elds of the wind-'- ing coils, are so disposed that failure of the inbarriers and not by creepage surfaces.

In the construction of each of the barriers it has in the past been necessaryl to build,up special washers, of a shape simulating that of the coil contour, by attaching to the main atrbody portion of the washer a plurality of anglepieces to'form the required right-angle edge. Because of the excessive amount of labor involved in making the angle edges and suitably attaching them to the washerbody, this form of construction has proven unduly expensive, as well as not being from the standpoint of insulation strength and mechanical rigidity.' My invention is directed to van improved form of construction for4 such washers which overcomes the -disadvantages named and which possesses further advantages to be particularized hereinafter. Generally stated, the object of my invention is to simplify the construction of insulation for transformers.

along the barrier Another object of Vmy invention is to reduceI filed October 6, 1931 andv assigned to' the Westinghouse Electric and Manby the puncture of thel the cost of assembling the insulating barriers in a transformer and to produce a simple and mefchanically rigid barrier structure.

A further object of my invention is to provide .a .barrier construction having improved insulation strength, particularly at the barrier corners. An additional object of my invention is to provide an insulating` barrier construction which will permit of free oil circulation between the barriers and the winding coils with which they are associated. y

C More specifically stated, an object -of my invention is to provide an improved and simplified form of construction for the end portions or washer assemblies of the insulating material barriers utilized by transformers of the surge proof construction.

Fullerboard has been adopted as being satisfactory material for use in the construction of insulating barriers l for the windings of surge proof transformers, which materialv has had a very extensive application in the general field of transformer insulation. As is known, fullerboard is made` from suitable wood pulp, which, in ahighly moistened or wet state is formed 'into 'sheets to heat and 4dried, thereby into a homogeneous mass possessing considerable mechanical rigidity. When fullerboard is properly moistened, therefore, it may revert to its original plastic or pulp-like-condition thereby permitting the physical shapeor contour of the moistened portions to be changed through an exceedingly wide4 range. A re-applilcation of heat and pressure may then be employed to restore the mechanical rigidity to the moistened portions to thereby cause board to retain themodified physical form.

In practicing my invention, described characteristic oi fullerboard in turning up the edges of the main washer or end portion of the insulating barrier by moistening the edges of the washerand inserting theminto a suitably formedV and heated process I am able to construct fullerboard washers having edges turned up at an angle of substantially 90 and I thereby eliminate the necessity of. attaching a large number of angle pieces to a main fiatv portion as has been necessary in the past. I

lMy invention will best be understood from the following description 'of specific embodiments thereof when taken in` conjunction with the accompanying drawings in* which:

Figure 1 is a view in horizontal section through the windings and core of a shell-type trans-# formel1` illustrating the coilsand insulating barriers arranged in accordance with one embodiment of transformer construction to which the I utilize the above mould. BY this y the fuller- 'i y structure illustrated in shown in Figs. 1 and 2.

improved washers of my invention are particularly applicable.

Fig. 2 is a sectional view of the transformer illustrated in Fig.' 1 taken along line II--II thereof.

Fig. 3y is a View of the high voltage winding assembly illustrated in Fig. 1 showing the manner in which the fullerboard washers of my invention are applied in building the nested insulating barriers about the winding coils.

Fig. 4 is av plan view, drawn to reduced scale, of one of the complete washers employed in the Fig. 3.

Fig. 5 is a sectional view of the washer, taken along the line V-V of Fig. 4, illustrating the turned-up edges of the washer.

Fig. 6 is a plan view of part of the washer illustrated in Fig. 4, showing certain details of construction thereof. x

Fig. 1 is a plan view of one of the inserts that may be used on the inside corners of the washer of Figs. 4, 5 and 6.

Figs. 8 and A9 are plan and elevational views of a modied form of construction'of the improved washer in which only the outer edge is turned up.

Figs. l0 and 11 `are similar views of a form of washer construction having only the inside edge turned up.

Figs. 12 and 13 are plan views illustrating the manner in which a complete Washer may be made up from a plurality of individually formed portions, and l Fig. 14 is a plan viewof a circular form of washer, having a turned up edge, that is suitable for use with core-type transformers.

` Referring to the drawings, the arrangement of the Acore and coils of a shell type transformer is 'In these figures, the core structure is shown as comprising two stacks of closed magnetic laminations 10 and 11, the adjacent sides of which form the winding leg of the transformer. The low voltage winding of the transformer is shown in two parts 16 and 17, surrounding and adjacent opposite ends of' the winding leg. -Between the low voltage windings are placed coils 20 to 26, inclusive, forming the high voltage winding.

Insulating barriers 30` to 36, inclusive, are shown in Fig. 1 in simplied form in the lefthand window of the core surrounding each of the several coils. For the sake of simplicity and to better show the connections between the coils, these insulating barriers are not shown in Fig. 1 in the right-hand window, that is, within the opening of the core structure 11, although it will be understood that they y extend continuously about the several coils as indicated in Fig. 2, It'

v will be noted that the coils proceeding from one end of the winding toward the other end, that is, from coil 20 to coil 26, are of decreasing external dimensions and increasing internal dimensions to accommodate the barriers 30 to 36, inclusive.

l In Figs. 1 and 2 lthe insulating barriers, 30 to 36 inclusive, have been represented in simplified form, no attempt being made to show the details of construction. Such details are shown in Fig. 3 in which only the portion of the high voltage winding coils 20 to 26, inclusive, included in the left-hand window of the core structure of Fig. l are illustrated. Each of the barriers, shown in Figs. 1 and 2 at 30 to 36, inclusive, is preferably constructed from fullerboard and comprises a pair of washers of the general type show n in Figs. 4 and 5 having turned-up edges. .'Ihus, for example, in the case of the barrier 30 directly associated with coil 20, the two associated washers are shown at 30 and 30, respectively, in Fig. 3, the turned-up edges thereof being disposed to face each other so that the barrier may be completed by the sheets 40 and 42 of insulating material. The sheet 40 is overlapped by the outer edges of washers 30 and 30'? and will be seen, as reference to the simplified showing of Fig. 2 will indicate, to extend continuously aroundthe outer periphery of coil 20. Likewise, the sheet 42 is overlapped by the inner edges of the washers 30' and 30 and will be seen to extend continuously around the inner .periphery of coil 20.

The insulatingbarriers associated with coils 2l to 26, inclusive, will be seen to similarly comprise fullerboard washers having turned-up edges and cooperating portionsof insulating material sheets so that further detailed description of them is deemed unnecessary.

As has been mentioned, each of these washers, one of which is illustrated by'Figs. 4 and 5, is preferably constructed from fullerboard or comparable insulating material. Fig. 6 is a detailed View of one corner ofthe washer shown in Fig. 4 more clearly illustrating the manner of construction. A iiat sheet of fullerboard is rst cut to the dimensions indicated by the dotted 105 outline in Fig. 6. The edges of this sheet are moistened to reduce vthe material to a plastic form, and are then bent to the desired angle, a suitably heated mould being applied to compress and dry the turned-up portion.

Due to the extreme change in contour of the fullerboard, at the inside corners of the Washer, which such turning-up operation necessitates, and to avoid tearing the material, it has been found preferable to out away a portion of the 115 horizontal inside edge, as at 50. The gap left at this corner may then readily be filled by the insertion therein ofa special angle piece of the form illustrated in Fig. 7. This angle piece, which has a turned-up edge 52 shaped to exactly 120 conform to the inside turned-up edge of the main washer, is then applied to the corner, and by suitably moistening, heating and compressing is efectively bonded,therein,' the nature of fullerboard being such as to permit such a fusion of its pulpy composition.

To provide for the ilow of insulating oil between the windings of the transformer and the associated insulating barriers, suitable spacing means maybe inserted therebetween as shown in Fig. 3. In the case of winding coil 20 these spacing members are illustrated in the form' of wavy spacers 60 and 61 placed on either side of the winding to separate it from direct contact with the surfaces ofthe adjacent barrier wash--l ers. In the plan view of one of the washers shown in Fig. 4 these wavy spacers are shown at '60', as attached to the inner surface of the washer. If desired, other spacing means, such as properly disposed rows of insulating material blocks, may be substituted for these spacers the blocks have the advantage of allowing the oil to circulate in all directions rather than restricting the iiow to one direction as do the wavy spacers illustrated.

In the showing of Fig. 3, the arrows are intended to indicate the paths available for oil flow. It will be noted that suitable ducts have been provided in the portions of the barrier invtermediate the oppositely faced washers through which the oil is permitted to pass. Preferably these ducts -are staggered in the manner shown.

Instead of turning up both edges of the washer as shown in Fig. 4, it is possible to construct it in a manner that only one of the edges is turned up. Such a modified construction is illustrated in Figs. 8 and 9 in which a section of the washer is shown having only the outer edge thereof turned up. Figs. ,l0 and 11 illustrate a section of a washer having only the inner edge thereof turned up.

In certain instances it may be desired to build a double edge washer of the type shown in Fig.

4 in two`` separate sections each` of which has.

only one edge thereof turned up. Thus, as shown in Fig. 12, the constructions of Figs. 8 and 10 may be combined to form the double edge assembly by properly fusing together the fullerboard material of the main flat portions of the sections as along the area shown as stippled in Fig. 12. The `composition of fullerboard, as :has been pointed out, is such as to readily allow such fusion, the necessary operations being to moisten the sections to be joined; tightly compress them together and thoroughly dry under pressure. In this operation the use of aibinding compound at the joint may be desired to improve the strength of the joint.

When the size of the turned-up edge washers is excessively large, it may be impossible to construct the entire washer from one continuous piece of fullerboard. In such situations the pieces to serve washer may be constructed in sections which are joined together in the manner indicated by the plan view of Fig. 13. In 13 the washer shown has been made up of vfour separate sec-A tions which are overlapped along the areas shown as stippled. As will be obvious from the showing of Fig. 13, the washer may be constructed'in halves, in quarters or in any other sub-division found convenient. Furthermore, this section type of construction applies not only to the double turned-up type Aof w ers typified by Fig. 4, but

also to the single turned-up edge washers illus.

trated in Figs. 8 and 10 and the combination thereof shown in Fig. 12. A very wide range of flexibility is, therefore, available in the manufacture of the complete washer.

As previously mentioned the turned-up edge fullerboard washers of my invention are not only applicable to shell type transformers, but may also be utilized with core type transformers. Because of the fact that the individual coils in such core type transformers are of a circular contour, the washers applied thereto will be circular' in form as shown in Fig. 14 rather than of the general rectangular design already described. The process of manufacture being essentially the same as that already explained, no further description of the washer of Fig. 14 is deemed-necessary.

In addition to the inner and outerturned-up edges of the washer, it will be desirable to attach to the main flat portion thereof suitable spacing devices to provide for oil iiow between thewasher and the winding coil. In Fig. 14 such spacing devices are indicated at 'I0 `in the form of radially attached strips.

It will'be apparent that by constructing an angle washer of the one-piece type', the resulting structure is much stifferI than when a main fiat washer has attached thereto a plurality of angle the same purpose. This rigidity is important to prevent sagging and the closing of the oil ducts, and furthermore, the advantage of eliminating joints or openings in the electrical path which the insulating barrier com prising the washer is intended to effectivelybreak up. The elimination of such joints improves, particularly at the barrier corners, the insulating eectiveness. Furthermore, the one-piece washer construction allows the insulating oil to more freely vcirculate since the anglel joints which would otherwise be present are eliminated at the corners.

Although I have shown and described certain specific embodiments of my invention I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the scope of the appended claims.

I claim as my invention:

l. In an electrical apparatus, the combination of a winding comprising. a stack of coils and a series of insulating barriers each of which is arranged to enclose a different number of. coils than the others, each of said barriers comprising a fullerboard washer having turned-up edges.

2. In an insulating barrier for a coil comprised by a multi-coil electrical winding, the combination of a plurality of insulating washers for the several coils having contours corresponding to those of the coils, one continuous edge of each washer being permanently bent at a right angle to parallel one side of said coil.

3. In an insulating barrier for a coil comprised by a multi-coil electrical winding, the combination of a plurality of insulating washers for the several coils each having a main fiat portion corresponding to the contour of the coil, the edges of said portion being bent at right angles to thereby parallel the sides of and thus surround said coil.

4. In an insulating barrier for acoil comprised by a multi-coil electrical winding, the combination of a f ullerboard washer having a contour simulating that of the coil, 'one -continuous edge of said washer being permanently bent at a right angle to parallel one side of said coil, said washer being built up from-` a plurality .of interiitting sections homogeneously merged together.

5. The method of manufacturing turned-upedge washers from sheet insulating material formed from pulp compressed and dried into a homogeneous mass, which consists in cuttingfrom the sheet a piece of material having dimensions greater than those desired in the main flat portion of the completed washer, reducing the material along an area thereof to a pulpy state by moistening, bending the material along said area to a desired angle, and simultaneously heating and compressing the material along the line of bend in said area to effect a drying thereof and a restoration of the material to its original mechanical rigidity.

6. The methodsof manufacturing turned-upedge washers' from sheet fullerboard which consists in cutting from the sheet a'piece of material having dimensions greater than those desired in the main flat portion of the completed washer, reducing the fullerboard, along an-area thereof, to a pulpy state by moistening, bending the material along said area to a desired angle, and simultaneously heating and compressing the fullerboard along the line of bend to effect a drying thereof and a restoration of the material to its original mechanical rigidity. 

